Fragments of brain cortex (piriform and visual) from donor mice at different stages of development will be transplanted to host mice in place of the partially or totally removed olfactory bulb. Since removal of the olfactory bulb induces degeneration of the olfactory sensory neurons, followed by their reconstitution and regrowth of their axons into the spared portions of the brain, we propose to study the interaction of transplanted cortical portions with the regrowing olfactory axons, and the interaction of the transplant's neurons with the caudally located spared portions of the host's brain. We intend to document with histological, ultrastructural and immunohistochemical methods the interaction occurring between the olfactory axons and the transplanted neurons as a way to study their level of plasticity and the degree of acceptance of the portions of the cortex which are related to (piriform cortex) or not related to (visual cortex) the olfactory system. We intend to see if the olfactory axons invade the transplant and if they modify, and to what extent, its organization in view of their established capacity (during embryogenesis) to play a major role in the development of the olfactory bulb from the wall of the prosencephalic vesicle. Moreover, we intend to see if formation of glomerular structures occurs in the transplant, and if the phenomenon is related to the age of the transplant and/or to its nature (visual/piriform cortex). The data collected could help us to estimate the degree of plasticity of the primary olfactory input and to evaluate the level of acceptance of the synaptic input by cortical cells in the frame of a new experimental model.